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Boiler help

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tommy69
tommy69 Member Posts: 2
I have a vaillant GA92 080 and I would like to adjust the boiler water temp to 135 degrees so I can run my under the floor PEX radiant heat at the recommended temperature but the lowest my aquastat will let me adjust it to is about 170 degrees. Is there a way I can adjust it somehow to go lower than that or a new part I could buy for it to make this possible? Any help appreciated

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  • Ironman
    Ironman Member Posts: 7,379
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    You need a mixing device to lower the SWT to the floor. You don't wanna let the boiler water temp stay that low; it will cause flue gas condensation which will rot your chimney and boiler out.
    What type of floor, wood, concrete, over pour?
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • tommy69
    tommy69 Member Posts: 2
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    Its all wood floor except the bathroom has tile. Is 170 too hot for the pex and floor?
  • Jamie Hall
    Jamie Hall Member Posts: 23,458
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    tommy69 said:

    Its all wood floor except the bathroom has tile. Is 170 too hot for the pex and floor?

    Yes. Listen to @Ironman and get and properly adjust the mixing valve.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Ironman
    Ironman Member Posts: 7,379
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    tommy69 said:

    Its all wood floor except the bathroom has tile. Is 170 too hot for the pex and floor?

    Absolutely too hot.

    Radiant heat requires proper design and there are a lot of variables that will determine what SWT is required. Typically, we don't want SWT to exceed 120*.

    Some more info from you will help determine what's needed:
    1. Is the radiant floor the sole source of heat?
    2. Was an accurate, scientific heat loss calculation done? Like a manual J?
    3. What's the size, spacing and length of the tubing runs?
    4. Were heat transfer plates installed on the tubing?
    5. Was O2 barrier tubing used?
    6. What about manifolds? What size pipe is supplying them?
    7. How many loops?
    8. What size pumps?
    9. Do you have a piping diagram?

    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.